Front opening wafer carrier with path to ground effectuated by door

ABSTRACT

A front opening wafer carrier formed principally of plastic and comprising an enclosure portion ( 20 ) and a door ( 24 ) has a path to ground with respect to the wafers ( 22 ), the path to ground effectuated by the door ( 24 ). The base “ground” may be provided at the machine interface upon which the carrier sits, or through the robotic arm that grasps, operates and moves the door ( 24 ).

This application claims the benefit of U.S. Provisional Application Ser.No. 60/333,682 filed Nov. 27, 2001, the same being incorporated hereinby reference.

BACKGROUND OF THE INVENTION

This invention relates to wafer carriers, more particularly it relatesto front opening wafer carriers with separable doors.

The processing of wafer disks into integrated circuit chips ofteninvolves several steps where the disks are repeatedly processed, storedand transported. Due to the delicate nature of the disks and theirextreme value, it is vital that they are properly protected throughoutthis procedure. One purpose of a wafer carrier is to provide thisprotection. During processing of semiconductor wafers or magnetic disks,the presence or generation of particulates presents very significantcontamination problems. Contamination is accepted as the single largestcause of yield loss in the semiconductor industry. As the size ofintegrated circuitry has continued to be reduced, the size of particleswhich can contaminate an integrated circuit has also become smaller,making minimization of contaminants all the more critical.

Wafer Carriers configured as enclosures for holding wafers intermediateprocessing steps are typically formed of numerous plastic componentsassembled together. The industry accepted configuration for largerwafers, that is 300 mm wafers, is to have an enclosure portion with alower machine interface configured as a kinematic coupling, an openfront closeable by a door, and stacked wafer shelves on the inside sidesof the enclosure portion. A door with a pair of latching mechanismssealingly closes the open front and will typically have wafer restraintsthat contact and restrain the forward edge of the wafers in theenclosure.

Conventional carriers used in the semiconductor industry may develop andretain static charges. Static buildup on carriers can causesemiconductor processing equipment to automatically shut down. It isdesirable to have a carrier with static dissipation characteristics tocontrol static charges.

A undesirable effect of static charges is exhibited when a chargedplastic part comes into contact with an electronic device or processingequipment of a significant different potential it may discharge in adamaging phenomena known as electrostatic discharge (ESD). Thesedischarges can be catastrophic during the processing of wafers intosemiconductors. Means are known to provide grounding of wafers forminimizing the occurrence of such discharges. See for example U.S. Pat.No. 5,711,082 to Nyseth, owned by the owner of the instant invention.

Contaminants in the form of particles may be generated by abrasion suchas the rubbing or scraping of the carrier with the wafers or disks, withthe carrier covers or enclosures, with storage racks, with othercarriers, or with the processing equipment. It is critical to keepcontaminants off of the wafers. The polycarbonate plastic shell of wafercarrier enclosures are known to naturally have a slightly negativecharge. Grounding of the wafer shelves and thus the wafers within theenclosure can render the wafers with no electric charge causingparticles to be attracted to the plastic enclosure rather than thewafers. See U.S. Pat. No. 5,944,194 to Gregerson, Gallagher, andWiseman, owned by the owner of the instant invention. The U.S. Pat. No.5,711,082 and 5,944,194 patents are incorporated herein by reference.These references provide background information, as well as theconfiguration and construction of wafer carriers, and illustrate meansof conventionally providing paths to ground.

SUMMARY OF THE INVENTION

A front opening wafer carrier formed principally of plastic andcomprising an enclosure portion and a door has a path-to-ground withrespect to the wafers effectuated by the door. The base “ground” may beprovided at the machine interface upon which the carrier sits, orthrough the robotic arm that grasps, operates and moves the door.Several alternate paths for the path to ground include the following:

1) From the robotic arm operating the door, for example, key receivingportions of said arm, through conductive components in the door such asthe latching mechanism, to a conductive wafer restraint that is mountedon the door for engaging the wafers.

2) From the machine interface upon which the carrier sits, to aconductive door contactor portion that contacts a portion of the doorwhen the door is moved into position on the carrier, to the conductivewafer restraints on the door.

3) From the machine interface upon which the carrier sits, to a moveableconductive active wafer restraint attached within the enclosure portion,to the wafers.

4) From the robotic arm operating the door, for example, the key insertportions of said arm, through conductive components in the door such asthe latching mechanism, to a conductive contactor portion extending fromthe door to an active wafer restraint mounted within the enclosureportion. The active wafer restraint may be actuated by a fixedconductive contactor portion or by an active contactor portion operatedby the latching mechanism of the door.

The conductive components may be formed, for example, from carbon fiberor powder filled polymers, metallic composites, conductive film coatedceramics, or conductive film insert molded polymer components.

An object and advantage of preferred embodiments of the invention isthat a path to ground for the wafers is established through the door.

An object and advantage of preferred embodiments of the invention isthat a path to ground for the door may be established before the waferscome into contact with the wafer restraints thereby minimizing thechance of a potential between the door and wafer causing a staticdischarge.

An object and advantage of preferred embodiments of the invention isthat potential between the door and wafers is eliminated before thecushions mounted on the door come into contact with the wafers.

An object and advantage of preferred embodiments of the invention isthat alternative or additional paths to ground are provided. Theconventional path to ground circuit is from the wafers through thecolumn of wafer support shelves to the lower machine interface which isgrounded through contact with grounded equipment or support base. Thealternative circuits are as described above. These may be in lieu of orsupplemental to the conventional path and further provide theelimination of potential with the wafer contacting components of thedoor.

DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of a front opening wafer container carrierin accordance with the invention herein.

FIG. 2 is a perspective view of a door of a wafer carrier in accordancewith the invention herein.

FIG. 3 is a perspective view of a door housing with latch mechanismcompartments exposed illustrating insert molded components providing apath to ground.

FIG. 4 is an exploded view of an enclosure portion of a wafer carrierwith latch mechanism exposed in accordance with the invention herein.

FIG. 5 is a perspective view of a components of a latching mechanism andkey suitable for the doors illustrated herein.

FIG. 6 is a perspective view of an enclosure portion and door of a wafercarrier with portions cut away illustrating an embodiment of theinvention herein.

FIG. 7 is a plan cross-sectional view of a portion of a wafer carrierillustrating a further embodiment of the invention.

FIG. 8 is a perspective view with sections cut-away of an enclosureportion of the wafer carrier of FIG. 7 in accordance with the inventionherein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1, and 2, a wafer carrier according to the inventionis illustrated and is principally comprised of an enclosure portion 20for holding wafers 22 and a door 24. The enclosure portion has a top 28with a robotic lifting flange 29, a bottom 30 with a machine interfacepiece 32, a pair of sides 34, 36, side handles 40, a door frame 44, anopen front 46, and a open interior 48. The door has an outside surface56, and inside surface 58, wafer restraints 60, latch compartments 64,66, and key slots 68, 70. Robotic arms 69 with keys for engaging thedoor are illustrated with dashed lines. The wafer restraints whenmounted on the door may be passive, that is, fixed on the door, oractive, as illustrated in U.S. Pat. No. 5,711,427, which is incorporatedherein by reference.

As illustrated in FIGS. 3, 4, and 5, a path-to-ground from the wafersmay be effectuated through the door latching mechanism 71 and waferrestraints. When used herein, “conductive and static dissipativepolymers” mean polymers with surface resistivity of less than aboutsquare and preferably less than 10⁸ ohms per square. The specificsurface resistivity appropriate may vary depending on the component andpath to ground circuit. Conductive plastic pieces 74, 76 may be insertmolded into the door housing 77 to provide a conductive path from themechanism to the mounting receptacles 84 for the wafer restraints. Thewafer restraints are formed of conductive material, preferably a carbonfilled polymer such as PEEK The insert molding of the conductive plasticpieces 74, 76 may be accomplished by insert molding of rigid pieces suchas illustrated in U.S. patent application Ser. No. 09/317,989, filed May25, 1999, and owned by the owner of this invention. Said application ishereby incorporated by reference. Also insert molded plastic conductivefilm may be utilized on components of the door to create the path toground 80 illustrated by the dashed lines. See U.S. Provisional PatentApplication 60//333,686, filed Nov. 27, 2001, and entitled Polymer FilmInsert Molding for Providing Electrostatic Dissipation, owned by theowner of this invention and incorporated herein by reference. The doorlatching mechanism 71 has a cammed hub 91 and a pair of link arms 93, 95that have latching portions 98, 99 that extend out apertures 100 in thedoor housing. The cammed hub will typically be molded of plastic withcarbon filler to provide static dissipative characteristics and has apair of cam surfaces 104 that are engaged by a cam followers 107 on thecammed hub. The cammed hub 91 also has a key hole 110 for receiving thekey 112 which would, pursuant to this embodiment of the invention, begrounded and part of a robotic operating arm. Thus, in this embodiment,the grounded key 112 is inserted into the key hole 110 and makes contactwith the conductive cammed hub. The cammed hub rotates on and contactsprotrusion 113 as part of the conductive piece of the door housing. Theconductive wafer retainers either may directly contact the conductivepiece of the door housing or a conductive mounting receptacle 84. Whenthe door is placed on the enclosure portion by the robotic arm, thelatching mechanism is grounded by the key and when the wafer restraintscontact the wafers they a path-to-ground is provided. In an alternativeembodiment the door housing may be made of conductive plasticeliminating the conductive piece.

Referring to FIG. 6, an alternative means of providing a path-to-groundeffectuated by the door is illustrated. In this embodiment, the machineinterface piece 32, is formed of conductive plastic and has three slots,not shown in this embodiment, forming a kinematic coupling in saidpiece. A conductive door contacting piece 190, configured as an arm,extends from the interface piece and is appropriately positioned tocontact the door when the door is closed onto the enclosure portion. Ina preferred embodiment, the arm may directly contact the waferrestraint, which will also be formed of conductive plastic. In a relatedembodiment a conductive plastic arm may extend from the door, beconductively connected to wafer restraints, and contact the groundedmachine interface piece as the door is closing. The arm in theseembodiments may be angled and have a thinned elongate portion tofacilitate bending during and after engagement with the respectivecomponents. Other embodiments may have curved compressible springsections. Thus, in this embodiment, the path-to-ground conductivecircuit is effectuated from the machine interface which is grounded onthe equipment or fixture upon which the container is placed. Thepath-to-ground circuit extends from the machine interface to the doorthrough a container-door bridging component configured as an arm, andthen to the wafer restraints. Preferably the container-door bridgingcomponent makes the connection between the door and the enclosureportion before the wafer restraints contact the wafers.

Referring to FIGS. 7 and 8, an alternative embodiment of the inventionis illustrated. In this embodiment the enclosure portion has a movablewafer restraint mechanism pivotally attached to the enclosure portionand configured as a pivotal elongate wafer contacting member 194. Thewafer contacting member or wafer restraint pivots to bring a waferengaging portion 96 into restraining and conductive contact with thewafers as illustrated in FIG. 8. The pivoting action of the waferrestraint is effected by an actuation member 198 extending from the doorand the conductive elongate wafer contacting member rotates about aconductive pin 201 engaged in apertures 202 on appropriate groundedsupport portions on the bottom of the wafer enclosure portion. A similarpin receiving aperture may be on the top of the wafer enclosure.Depending on the configuration of the wafer restraint, the actuationmember can be passive, to actuate the wafer restraint by simply closingthe door, or can be active to operate by actuation of the latchingmechanism 199. When the door is moved into the closure position, thedoor actuation member 198 engages with the actuation member to move sameinto an contact and restraining position with the stack of wafers. Inthis embodiment, the further door wafer restraints 204 may or may not beutilized. If utilized, the door wafer restraints may be grounded by wayof actuation member engaging the grounded elongate wafer contactingmember.

Thus the invention functions as follows: when the enclosure portion hasa wafer stack or wafer positioned therein, the door is moved into place,either manually or by robotic means. In the preferred embodiment, thewafer restraints are grounded by completion of a path to ground beforethe wafer restraints come into contact with the wafers.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof, and it is,therefore, desired that the present embodiment be considered in allrespects as illustrative and not restrictive

1. A wafer container comprising an enclosure portion with an open front,a door for sealingly closing the open front, the container portioncomprising a plurality of shelves for holding a vertical stack of spacedhorizontal wafers, the door having a door housing, a wafer restraintformed of conductive plastic with a plurality of wafer engagementmembers positioned on the door housing, said plurality of waferengagement members adapted to engage said stack of spaced horizontalwafers when said door is positioned so as to sealingly close the openfront of said enclosure portion, and a latching mechanism containedwithin the door housing, the latching mechanism having a key receivingportion on a front side of the door with a key receiving slot, the doorhousing and latching mechanism having conductive portions electricallyconductively connecting said wafer restraint with said key receivingportion so that when a grounded key is inserted into the key slot toengage the key receiving portion, the wafer restraint is grounded thoughsaid conductive portions.
 2. The wafer container of claim 1 wherein doorhousing is formed primarily of nonconductive plastic.
 3. The wafercontainer of claim 2 wherein a conductive piece is positioned in thedoor housing by way of insert molding and said conductive piece andwherein the path to ground extends through said conductive piece.
 4. Awafer container comprising an enclosure portion with an open front, adoor for sealingly closing the open front, the container portioncomprising a plurality of shelves for holding a vertical stack of spacedhorizontal wafers, the door having a door housing, a wafer restraintformed of conductive plastic with a plurality of wafer engagementmembers positioned on the door housing, and a latching mechanismcontained within the door housing, the latching mechanism having a keyreceiving portion, the key receiving portion electrically conductivelyconnected to the wafer restraint.
 5. The wafer container of claim 4wherein the door housing is primarily formed from a non conductiveplastic and wherein the door is further comprised of a latchingmechanism and wherein a path to ground extends through at least onelatching mechanism component.
 6. A wafer container comprising anenclosure portion with an open front, a door moveable from a closedposition whereby the door is sealingly closing the open front, to anopen position whereby the door is separated from the enclosure portion,the enclosure portion comprising a plurality of shelves for holding avertical stack of spaced horizontal wafers, a wafer retainer made fromelectrically conductive material and adapted to contact said wafers, anda groundable machine interface on a lower side of the enclosure portion,the wafer container further comprising an electrically conductiveconnection portion bridging between the door and the enclosure portionwhen the door is in the closed position, the connection portion formingpart of a conductive path to ground circuit between the wafer retainerand the groundable machine interface when the door is in the closedposition.
 7. The wafer container of claim 6, wherein the conductiveconnection portion comprises an arm extending from one of the door andenclosure portion to the other of the door and enclosure portion whenthe door is in the closed position.
 8. The wafer container of claim 7,wherein the arm extends from the door and is operatively connected tothe latch mechanism.
 9. The wafer container of claim 7 wherein theconductive connector is fixed to the door and the enclosure portionfurther comprises a pivotal wafer restraint actuated by said conductiveconnector when the door is moved into the closed position.
 10. The wafercontainer of claim 9 wherein the pivotal wafer restraint is moveablebetween an obstructing position and a nonobstructing position withrespect to insertion and removal of wafers from the plurality ofshelves.
 11. A method of providing a path to ground through the door ofa wafer container, the wafer container comprising an enclosure portionwith a open front for insertion and removal of wafers and a door forsealingly closing the open front, the door having a wafer restraint forrestraining wafers held in the enclosure portion, the method comprisingthe steps of: forming an electrically conductive circuit through thedoor to the wafer restraints utilizing conductive plastic, completingthe conductive circuit to the wafer restraints with ground before thedoor is moved into a closed position and before the wafer restraintsengage the wafers, and moving the door into the closure position wherebythe grounded wafer restraints engage the wafers.
 12. The method of claim11, further comprising the step of completing the conductive circuitwith ground by inserting a grounded key into a key receiving portion ofthe door.
 13. The method of claim 11, further comprising the step ofcompleting the conductive circuit with ground by utilizing a bridgingconductive component extending between the door and a grounded portionof the container portion.
 14. The method of claim 13, further comprisingthe step of actuating a wafer restraint pivotally mounted in theenclosure portion with the bridging conductive component.
 15. A methodof providing a path to ground through the door of a wafer container, thewafer container comprising an enclosure portion with a open front forinsertion and removal of wafers and a door for sealingly closing theopen front, the wafer container having a wafer restraint for restrainingwafers placed in the enclosure portion, the method comprising the stepsof: forming a conductive circuit through the door to the waferrestraints utilizing conductive plastic, completing the conductivecircuit to the wafer restraints with ground before the door is movedinto a closed position and before the wafer restraints engage thewafers, and moving the door into the closure position whereby thegrounded wafer restraints engage the wafers.
 16. The method of claim 15,further comprising the step of completing the conductive circuit withground by inserting a grounded key into a key receiving portion of thedoor.
 17. The method of claim 15, further comprising the step ofcompleting the conductive circuit with ground by utilizing a bridgingconductive component extending between the door and a grounded portionof the container portion.
 18. The method of claim 17, further comprisingthe step of actuating a wafer restraint pivotally mounted in theenclosure portion with the bridging conductive component.
 19. A wafercontainer comprising an enclosure portion with an open front, a doormoveable from an open position whereby the door is separated from theenclosure portion to a closed position whereby the door is sealinglyclosing the open front, the container portion comprising a plurality ofshelves for holding a vertical stack of spaced horizontal wafers, thewafer container including a path to ground circuit extending throughconductive plastic components and the path to ground circuit is openwhen the door is in the open position and wherein the closing of thedoor effectuates the closing of the path to ground circuit.
 20. Thewafer container of claim 19 wherein the path to ground circuit extendsthrough a latching mechanism contained in the door.
 21. A wafercontainer comprising an enclosure portion with an open front, a doormoveable from a closed position whereby the door is sealingly closingthe open front, to an open position whereby the door is separated fromthe enclosure portion, the enclosure portion comprising a plurality ofshelves for holding a vertical stack of spaced horizontal wafers and agroundable machine interface on a lower side of the enclosure portion,the door including a plurality of electrically conductive waferrestraints adapted to engage the wafers when the door is in the closedposition, the wafer container further comprising an electricallyconductive connection portion bridging between the door and theenclosure portion when the door is in the closed position, theconnection portion forming part of a conductive path to ground circuitbetween the wafer retainers and the groundable machine interface whenthe door is in the closed position.
 22. The wafer container of claim 21connection portion comprises an arm extending from one of the door andenclosure portion to the, wherein the conductive other of the door andenclosure portion when the door is in the closed position.